The present invention relates generally to X-ray focusing and, more particularly, to reflective lenses and systems which convert X rays from divergent sources into parallel or convergent radiation for a variety of applications.
Translation of X-rays from divergent sources into parallel beams and converging rays is subject to well-known limitations relating to Bragg diffraction theory. Focusing optics for x-rays have been based on Johann or Johansson methods applied to curved monolithic crystals. See, for example, Advances in X-Ray Spectroscopy, Eds. C. Bonnelle and C. Mande (Oxford, U.K., 1982). More recently, it has been shown that x-ray diffractors with doubly curved crystals can provide relatively greater throughput. For example, a spherical diffractor with a stepped surface has been designed at constant height conditions to provide a significantly greater solid angle aperture than achievable with a spherically curved crystal. See Witry et al., xe2x80x9cProperties of curved x-ray diffractors with stepped surfacesxe2x80x9d, J. Appl. Phys., 69, pp.3886-3892, (1991) which discusses problems associated with practical manufacture of high-efficiency x-ray diffractors.
A diffractor may also be formed with a few pseudo-spherical curved dispersive elements. See Marcelli et al. xe2x80x9cMultistepped x-ray crystal diffractor based on a pseudo-spherical geometryxe2x80x9d, SPIE Vol. 3448, July 1998. See, also, Mazuritsky et al. xe2x80x9cA new stepped spherical x-ray diffractor for microbe analysisxe2x80x9d, SPIE Vol. 3449, July 1998. Even with these advances, formation of satisfactory lens systems for x-ray optics has been limited by the size of practical crystal surfaces and the extent to which such surfaces can be conformed to a desired curvature.
Consequently, x-ray optics have so far only provided as throughput a relatively small portion of the energy available from x-ray sources. This has rendered systems applications relatively large and inefficient. If larger amounts of x-ray energy could be transformed into parallel or convergent radiation, many potential applications of x-ray energy would become commercial realities. For example, with higher efficiencies, x-ray systems could become more portable and therefore more mobile.
In one form of the invention a reflective lens is provided with at least one curved surface formed of polycrystalline material. In an example embodiment a lens structure includes a substrate having a surface of predetermined curvature and a film formed along a surface of the substrate with multiple individual members each having at least one similar orientation relative to the portion of the substrate surface adjacent the member such that collectively the members provide predictable angles for diffraction of x-rays generated from a common source. In another embodiment a lens structure is formed with a polycrystalline film formed along a surface and having a curved plane fiber texture orientation.
In another embodiment of the invention a Bragg reflecting surface is formed by providing a substrate having a surface of predetermined curvature and forming a polycrystalline layer over the surface with the majority of individual crystalline grains having a common orientation with respect to the underlying substrate surface.
In still another embodiment of the invention a device for translating x-rays includes a polycrystalline surface region having crystal spacings suitable for reflecting a plurality of x-rays at the same Bragg angle along the region and transmitting the reflected x-rays to a reference position.
A system is also provided for performing an operation with x-rays. In one form of the invention the system includes a source for generating the x-rays and a polycrystalline surface region having crystal spacings suitable for reflecting a plurality of x-rays at the same Bragg angle along the region and transmitting the reflected x-rays to a reference position. An associated method includes providing x-rays to a polycrystalline surface region having crystal spacings suitable for reflecting a plurality of x-rays at the same Bragg angle along the region and transmitting the reflected x-rays to a reference position and positioning a sample between the surface region and the reference position so that x-rays are transmitted through the sample. In another embodiment the method includes providing x-rays to a polycrystalline surface region having crystal spacings suitable for reflecting a plurality of x-rays at the same Bragg angle along the region and transmitting the reflected x-rays to a reference position and positioning a sample at the reference position so that x-rays strike the sample.